Ocean Floor

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Ocean Floor
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Continental Margin

• An underwater extension of the continents
• Comprises about 1/3 of the Atlantic Ocean Floor
• Divided into three parts shelf, slope and rise
• Two types of margins Active and Passive

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Active Margins

• Sides of continents facing CONVERGING plates
  boundaries
• volcanic activity common
• earthquake activity common
• steeper offshore slopes
• narrow continental shelf
• Found along the continents that border the
  Pacific Ocean

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Passive Margins

• Sides of continents facing DIVERGING plate
  boundaries
• no volcanic activity
• no/little earthquake activity
• gentle offshore slopes
• wide continental shelf
• Found in eastern North and South America,
  western Africa, and western Europe

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The Continental Shelf

• Shallow submerged extension of a continent (0200
  m)
• Close to land and is economically important
• Relatively flat (about 2 m every kilometer)
• Extends about 300 km from the continent, but can
  be further or closer depending on the type of
  plate activity

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Continental Slope

• Transition between the continental shelf and the
  deep ocean floor
• Sharp change in slope occurs at the shelf break
• Has a typical inclination of about 70 meters per
  kilometer (much steeper than the continental
  shelf)

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Continental Rise

• Composed of sediments derived from the
  continents, shelf and slope
• More developed off the mouths of large rivers,
  which deposit sand and other sediment material
  onto the rise.

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Submarine Trenches

• Deep troughs in the abyssal floor usually up to
  6000 m
• Trenches are formed when oceanic plates are
  subducted one plate is forced under another
  plate. (Converging Fault)
• Most trenches are found in the Pacific Ocean
  (Pacific Ring of Fire regions of great volcanic
  activity)
• Challengers Deep is the deepest trench ever
  found it is 11 km deep!

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Abyssal Floor

• Very flat and featureless sediment-covered ocean
  floor much like a desert on the ocean floor
• These features usually exist between mid-ocean
  ridges and the continental shelves
• Deepest part of the ocean other than the trenches
• Average depth of 4000 m.
• No light, near freezing, extremely high water
  pressure

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